Self-stabilized encapsulated imaging system

ABSTRACT

Wireless capsule endoscope technology has been used to image portions of the gastrointestinal (GI) tract, particularly the small bowel. However in other GI organs, especially those having larger-lumens, the capsule may become destabilized and tumble, precluding meaningful interpretation of the acquired images. The present invention describes a method and apparatus for permitting capsule imaging of organs having larger-lumens without tumbling, and includes an outer shell surrounding the capsule that targets the colon, as an example. Once the colon has been reached, the shell breaks or dissolves, and allows expansion of expandable materials attached to each end of the capsule, thereby stabilizing the capsule in the targeted organ, while permitting it to be moved by peristalsis and/or other means for locating the capsule. Imagers and light emitting diodes (LEDs) are activated during the expansion process, and enable overlapping of images. The capsule is moved through the colon, taking images at chosen frame rates with data being wirelessly transmitted by means of an RF transmitter, and is eventually expelled from the body.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit under 35 USC 119(e) of United Statesprovisional patent application No. 60/650,278 filed Feb. 4, 2005.

FIELD OF THE INVENTION

The present invention relates generally to imaging of thegastrointestinal organs and, more particularly, to the imaging ofgastrointestinal organs using a self-orienting, capsule-based imagingsystem.

BACKGROUND OF THE INVENTION

Recent advances in low-power complementary metal-oxide silicon (CMOS)imagers, mixed signal application specific integrated circuit (ASIC) andwhite light emitting diodes (LEDs) has led to a swallowable videocapsule for endoscopy [See, e.g., Arkady Clukhovsky, “Wireless CapsuleEndoscopy” , Sensor Review, 23, no.2, pp. 128-133 (2003).].Capsule-based imaging of gastrointestinal organs was introduced in 1997[See, e.g., Iddan et al., “In Vivo Video Camera System”, U.S. Pat. No.5,604,531, Feb. 18, 1997.], and has since become a preferred imagingmodality for the small intestine due to its non-invasiveness and itscapability for wirelessly delivering video imaging information [See,e.g., Roberto de Franchis et al., “Small Bowel Malignancy,”Gastrointest. Endoscopy Clin. N. Am., Vol. 14, pp. 139-148 (2004); andDoron Fischer et al., “Capsule endoscopy: the localization system”,Gastrointest. Endoscopy Clin. N. Am., 14, pp. 25-31 (2004).] Thewireless capsule endoscope presently sold by Given® Engineering LTD,Yoqneam, Israel as the M2A™ Swallowable Imaging Capsule, is 11 mm by 26mm, pill-shaped, and contains 4 longitudinally positioned light emittingdiodes (LEDs), a longitudinally disposed CMOS imager, lenses, a batteryand an antenna/transmitter.

Application of this technology to other gastrointestinal organs,including the esophagus, the stomach, the duodenum, and the colonexposes the difficulty that, for organs having significantly largerlumens than the small intestine, the average diameter of which is about2.5 cm, the imaging capsule may tumble during its passage through alarger-lumen organ since the capsule lacks a mechanism for laterallystabilizing itself, thereby precluding meaningful interpretation of theacquired images.

Accordingly, it is an object of the present invention to provide anapparatus and method for facilitating capsule-based imaging of thegastrointestinal tract.

Another object of the invention is to provide an apparatus and methodfor imaging the larger-lumen gastrointestinal organs from whichmeaningful images may be generated.

Additional objects, advantages and novel features of the invention willbe set forth, in part, in the description that follows, and, in part,will become apparent to those skilled in the art upon examination of thefollowing or may be learned by practice of the invention. The objectsand advantages of the invention may be realized and attained by means ofthe instrumentalities and combinations particularly pointed out in theappended claims.

SUMMARY OF THE INVENTION

To achieve the foregoing and other objects, and in accordance with thepurposes of the present invention, as embodied and broadly describedherein, there is provided according to an aspect of the invention anapparatus for imaging walls of a gastrointestinal organ, the apparatuscomprising a swallowable capsule, an imaging system carried by thecapsule, an expandable material attached to the capsule by acontrollable releasing mechanism; and the expandable material beingexpandable to stabilize the capsule in the gastrointestinal organ. Inother aspects of the apparatus, the capsule has a cylindrical portion.According to another aspect of the invention, the capsule has a firstend and a second end; a first expandable material attached to the firstend of the capsule; a second expandable material attached to the secondend of the capsule; an outer component for sealing the capsule, thefirst expandable material and the second expandable material, andadapted to dissolve or break within a targeted gastrointestinal organ,but not in other gastrointestinal organs, thereby permitting swelling ofthe first expandable material and the second expandable material suchthat the capsule is laterally stabilized within the targetedgastrointestinal organ while being able to moved through thegastrointestinal organs by peristalsis and/or other means. In stillfurther aspects of the invention there are provided as part of theimaging system at least one light emitting diode adapted forilluminating a portion of the interior of the targeted gastrointestinalorgan; at least one imager for imaging the internal wall of the targetedgastrointestinal organ, and generating signals bearing the images of theinternal wall; a wireless transmitter; and means for controlling theoperation of the at least one light emitting diode and the at least oneimager, for receiving the signals from the at least one imager, and fordirecting the signals to the wireless transmitter for transmission outof the targeted gastrointestinal organ.

In another aspect of the invention, and in accordance with its objectsand purposes, the apparatus for imaging gastrointestinal organs mayinclude a combination of: a transparent cylindrical capsule having afirst end and a second end; a first expandable material attached to thefirst end of the capsule; a second expandable material attached to thesecond end of the capsule; means for sealing the capsule, the firstexpandable material and the second expandable material, and adapted todissolve or break within a targeted gastrointestinal organ, but not inother gastrointestinal organs, thereby permitting swelling of the firstexpandable material and the second expandable material such that thecapsule is laterally stabilized within the targeted gastrointestinalorgan while being able to be moved through the gastrointestinal organsby peristalsis and/or other means; means for illuminating a portion ofthe interior of the targeted gastrointestinal organ; at least one imagerfor imaging the internal wall of the targeted gastrointestinal organ,and generating signals bearing the images of the internal wall; meansfor wirelessly transmitting the signals bearing images of the internalwall out of the targeted gastrointestinal organ; means for controllingthe operation of the means for illuminating and the at least one imager,for receiving the signals from the at least one imager, and fordirecting the received signals to the means for wirelessly transmitting.

In still another aspect of the present invention, and in accordance withits objects and purposes, the method for imaging gastrointestinal organshereof includes the steps of: introducing a capsule adapted forobtaining images of the internal walls of structures through which itpasses and for wirelessly transmitting these images, into thegastrointestinal tract of a patient; moving the capsule through thegastrointestinal tract to an organ to be imaged; stabilizing the capsulein the organ of interest such that the capsule does not tumble;activating the imaging function of the capsule in the organ to beimaged; transmitting the images obtained by the capsule to an imageprocessor external to the patient; and moving the capsule out of thegastrointestinal tract.

Benefits and advantages of the present invention include, but are notlimited to, the ability to obtain accurate and interpretable images ofthe interior of a targeted gastrointestinal organ.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are incorporated in and form a part ofthe specification, illustrate embodiments of the present invention and,together with the description, serve to explain the principles of theinvention. In the drawings:

FIG. 1 is a schematic representation of an embodiment of the presentwireless endoscope capsule showing, in particular, the casing, theinterior components and the expandable material thereof.

FIG. 2 is a schematic representation of an embodiment of the apparatusfor data collection hereof via a serial port, and transmission thereoffrom the RF transmitter in the capsule of FIG. 1 to a receiver outsideof the patient.

FIG. 3 shows an example of the timing diagram for an imager and a lightemitting diode in a frame captured by the imager.

FIG. 4 is a schematic representation of the ends of the casing shown inFIG. 1 hereof, illustrating the expandable material.

FIGS. 5 AND 6 are schematic representations of details of the expandablematerial.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS OF THE INVENTION

Briefly, the present invention includes an apparatus and method forimaging gastrointestinal organs from which meaningful images may begenerated. The apparatus hereof comprises a wireless imaging capsulehaving an outer component that dissolves or breaks in the targetedorgan, thereby permitting swelling of expandable materials disposed oneach end of the capsule. As a result, the capsule is oriented andself-stabilizing against tumbling. At about the time of the expansionprocess, during this process or just afterwards, imaging components inthe capsule are activated. These may include light emitting diodes(LEDs) for illuminating the interior of the organ of interest, and imagesensors. The oriented and stabilized wireless capsule endoscope can thenprovide images from which details of the inner walls for organs havinglarge lumens can be reconstructed. Although the colon has been chosen asan example of a large-lumen organ in the following description,application of the present invention is not limited to this organ.

Reference will now be made in detail to the present preferredembodiments of the invention examples of which are illustrated in theaccompanying drawings. In what follows, identical callouts will be usedfor similar or identical structure. Turning now to FIG. 1 hereof, shownis a schematic representation of self-stabilizing capsules, 10, of thepresent apparatus which may include an outer protective coating or shell11 (FIG. 5), which dissolves or breaks after capsule 10 enters thegastrointestinal organ to be imaged.

At least one imager, 12, and at least one white light emitting diode(LED), 14, circumferentially arranged on capsule 10 are then activated.It should be mentioned that complementary metal-oxide silicon (CMOS)imagers may be used in accordance with the teachings of the presentinvention. At about the same time that the protective coating or shellbreaks or dissolves the expandable parts, 16 a and 16 b, of capsule 10expand and stabilize the capsule in the lumen of the colon. The capsuleis moved through the colon by peristalsis. At least one radio-frequency(RF) transmitter, 18, transmits the acquired images at an appropriateframe rate to an external receiver and data processor adapted forreproducing the received images, also not shown in FIG. 1. Batteries, 20a and 20 b, furnish electrical power to the electronic components ofcapsule 10. Controller, 22, directs the functioning of the components ofcapsule 10, including directing transmitter 18 to communicate datacollected by imagers 12 to an external receiver, not shown in FIG. 1.Capsule casing, 24, provides protection for the capsule components fromgastrointestinal fluids and from mechanical destruction, and furnishesscaffolding from which the components can be effectively mounted anddeployed. A system may also be used, such as a magnetic location system,for locating the capsule in the targeted gastrointestinal organ.

Having generally described the components of capsule 10, the followingdescription provides greater detail thereof.

Outer Component: The outer component may include a capsule or a coatingwhich remains intact throughout the capsule's movement through the GItract until the colon, or other targeted gastrointestinal organ, hasbeen reached. Capsules are preferred by patients since they aregenerally easy to swallow. Once within the colon, the outer componentdissolves or breaks to allow the expandable component to enlarge andstabilize the capsule. The imaging components are activated after thisoccurs. The outer component may be fabricated from a colon-targetingmaterial that would be stable in the stomach and small intestine, butwould dissolve or break once in the colon. For imaging the smallintestine, as another example, a small-intestine targeting materialwould be used. In U.S. Pat. No. 5,688,776 for “Crosslinkedpolysaccharides, process for their preparation and their use,” which wasissued to Bauer et al. on Nov. 18, 1997, certain crosslinkedpolysaccharides suitable for colon-targeting due to their enzymaticdegradability by the microflora of the large intestine are described. Itwas also disclosed in Bauer et al. that using pH alone to select anorgan would be insufficient to target the colon as opposed to the smallintestine, since there is only a small difference in pH values betweenthe small intestine and the large intestine. Crosslinkedpolysaccharides, by contrast, are stable in the small intestine sincethey are not attacked by amylases found in the small intestine. A usefulcolon-targeting material chosen for the present design would thereforebe a crosslinked polysaccharide, an example of which is crosslinkeddextran.

It has been found that crosslinked dextran capsules provide a bettercolon-specific drug release by limiting diffusional release in the upperGI tract. Such capsules also degrade more rapidly in the colon [See,e.g., H. Brondsted et al. “Crosslinked dextran-a new capsule materialfor colon targeting of drugs,” Journal of controlled Release, 53, pp.7-13 (1998)], when compared to matrix systems. It was further found thatdextran capsules quickly break and release drugs as a dose dump inexperiments simulating the arrival of the capsule in the colon [See,e.g. Brondsted et al., supra].

Imaging Components: Imaging components include: (a) a casing; (b)imagers; (c) LEDs;

(d) at least one radiofrequency (RF) transmitter; (e) at least onebattery; and (f) a control unit. Casing: The casing may be made of atransparent, inert material through which light from the LEDs canilluminate the organ features such that these features can be identifiedby the imagers. The material should also have sufficient structuralstrength so as not to break in the gastrointestinal environment.Polymeric materials including polycarbonates, and polyetherimide [See,e.g., Long, “Self-propelled, intraluminal device with electrodeconfiguration and method of use,” U.S. Patent application No. 0125788A,filed on July 3, 2003.] are known by those skilled in the art to havethese properties. A generally cylindrical shape for the casing enabledthe prediction of the increase in volume of the expandable material.

Imagers: At least one imager (there may be X imagers, where X disposedin the capsule, captures images of the walls of the colon at aparticular position in the snapshot mode. All of the imagers takepictures of the interior of the colonic wall at same position along thelength of the colon, but of different portions of the wall within aparticular colonic wall band, before being moved to another position byperistalsis. For example, three such imagers may be circumferentiallypositioned, each providing an imaging angle of 120° when associated withappropriate optical lenses, thereby providing 360° imaging of a band ofthe colonic wall. With a larger number of imagers, the overlap of thecaptured images will be greater, and the composite images of eachcolonic band should be improved. However, since the capsule should beable to be swallowed by a patient, and should be able to reach thecolon, the dimensions of the capsule casing are constrained. Therefore,the number of imagers is limited due to space constraints.

It is known that the propagation velocity differs in various sections ofthe colon. The time resolution of the sampling of the imagers is chosento ensure that meaningful data are collected; that is, the minimumnumber of frames required for a particular distance traveled depends onthe speed of the capsule in the location of the fastest velocity in thecolon. The imagers may be directed by a controller to record images witha desired time resolution. The time resolution of the sampling of theimagers defines the power needed per frame, which in turn determines thenumber of imagers that can be used for a certain amount of powersupplied. Dynamic time resolution for image sampling may be achieved ifa three-axis accelerometer, such as an Analog Devices, Inc., ADXL330,accelerometer, as an example, is integrated into the capsule, so thatthe velocity of propagation is monitored and the time intervals betweensuccessive image snapshots are adjusted accordingly.

As will be described hereinbelow, 3 LEDs may be used; therefore based ongeometrical considerations, 3 CMOS imagers may be used. It may also beshown that a useful maximum width for the imagers is about 9.5 mm.Snapshot CMOS imagers between ⅓ and ½ in. in size would fit inside theproposed capsule. Some commercially available snapshot imagers fromMicron Technology Inc. of Boise Idaho have the dimensions 0.5×0.55 in.[See, e.g., Micron Technology Inc., CMOS Image Sensors, 2004]. Forexample, the Micron Technology imager MT9V 403 is a 0.3 mega-pixel,capable of 0-200 fps and requires 39.4 mA at 200 fps for a 3.3 V powersupply. This imager may be used in accordance with the presentinvention. Lenses providing a sufficiently large imaging angle may beemployed in conjunction with the imagers.

Light Emitting Diodes LEDs: The circumferentially disposed LEDs providelight for capturing images over a 360° range. Furthermore, due to spaceconstraint in the approximately 11 mm diameter casing, the LEDs have tobe small and yet provide enough luminous intensity for useful images tobe obtained. It is desirable that luminous intensities should besufficient for illumination in the region of the colon where the lumenis largest; that is, the cecum. The LEDs are synchronized with theimagers through a control system described below such that the imagesfrom the circumferentially arranged imagers can be simultaneouslycaptured. The power required by the LEDs clearly depends on the numberand type of LEDs used.

With the availability of 180° -viewing angle surface-mounted LEDs, twoLEDs may be used to cover a 360° viewing range; however, the intensitiesof such LEDs are presently too low [See, e.g., Fairchild SemiconductorCorporation, 2001. (Online) Available:http://www.fairchildsemi.com/products/opto/ Aug. 20, 2004.]. Therefore,for the proposed apparatus, 3 surface-mounted LEDs having viewing anglesof between about 120° and 140° degrees may be chosen. Light emittingdiodes having these characteristics are available in small sizes, can besurface mounted, and can be disposed in an 11 mm diameter capsule [See,e.g., Fairchild Semiconductor Corporation, supra.]. Light emittingdiodes suitable for use in the present invention may also havefrequencies and duty cycles that match the time resolution and imagetransfer rates of the image sensors.

Radiofrequency (RF) transmitter; At least one RF transmitter equippedwith an appropriate antenna is used to wirelessly transmit data from theimagers to an external receiver, also equipped with an appropriateantenna. There may be the same number of RF transmitters (X≧1) totransmit the data as there are imagers or, if data from the imagers aretime-multiplexed so that the data collected is serially directed to theRF transmitters, fewer transmitters can be used to save power and space.FIG. 2 is a schematic representation of one embodiment of datacollection using a serial port. At least one RF transmitter 18 may besynchronized with the imagers 12 a-12 x and LEDs 14 through controller22 that may be integrated into one application specific integratedcircuit (ASIC) chip. Data collection from imagers 12 may be multiplexedserially by controller 22 to an RF transmitter. There will be adifferent delay in data transmission for each imager, in order to enablesuch serial multiplexing. For example, a first imager may transmit datawhen it is ready, a second imager may transmit its data after a delayhaving duration, t, where t is the time required by the first imager totransmit its data, a third imager may transmit data after 2 such delays,etc. The data collected is directed to RF transmitter 18 fortransmission to data processor, 26, located external to the patent andincluding RF receiver, 28, from which received data is directed bycontroller, 30, to data logger, 32, for storage and readout.

For the present design, the MAX1472 amplitude shift-keying (ASK)transmitter from Maxim Integrated Products, Inc. (Sunnyvale, Calif.)would be useful. It is a phase-locked-loop (PLL) transmitter whichoperates in the 300 MHz to 450 MHz frequency range. The transmitter hasa current consumption of less than 9 mA and is in a 3 mm×3 mm SOT23package. Assuming that the images are time-multiplexed in accordancewith the teachings of the present invention, one transmitter may bechosen for the proposed design. An ASK superheterodyne receiver,MAX1473, may be used to receive the transmitted data direct to a datalogger, as illustrated in FIG. 3.

Controller: The synchronization of the image sensors and LEDs can beachieved using a controller which can be a separate entity or integratedin one ASIC chip with the RF transmitter. Microcontrollers,field-programmable gate arrays (FPGAs) and digital signal processing(DSP) technologies can be used for this purpose.

The controller provides the signals for operating both the imagers andthe LEDs based on a chosen sampling and data transfer rate. Additionalprocessing may be required to make efficient use of the transfer rate ofthe image data. Since factors such as the propagation velocity throughthe colon and the total transit time in the colon vary amongindividuals, in the situation of an individual having a slow propagationvelocity while the time resolution of the imager is being determined bythe fastest possible velocity, the imager would sample unnecessarilywith the capsule moving slowly. The power initially allocated for aparticular sampling rate might not then be sufficient for the entiretravel of the capsule in the colon.

The difference in propagating velocities for each individual may beaccommodated by introducing a control system having a feedback loop sothat the sampling rates of the imagers are adjusted according to theactual propagating velocity of the capsule. This method uses the powerefficiently and is not directly dependent on the propagating velocity,but on the length of the colon. That is, sampling may be performed overthe length of travel, rather than at a uniform sampling resolution,making the design more adaptable to any individual.

Batteries: Power supplied by the batteries may determine the number ofimagers and

LEDs that can be used, since it is desirable to image the entire colon.Based on the average transit time, the amount of time, T, which thebatteries should operate can be chosen. The fastest propagating velocityin the colon, V, and the time resolution of the sampling process,defines a sampling distance, R, at which views of the colon segments areobtained. The total number of frames, D, can then be calculated from theequation D D=V·T/R. For Z (Z≧1) batteries, the power consumption perframe of one imager, Y (.Y>0), can be calculated. The total powerconsumption for Z batteries for X (X≧1) imagers for a single frame isX·Y. Therefore, values for X, Z and R can readily be selected. Tominimize the power required by the LEDs, these devices can be pulsed for1/N s in synchronization with a chosen frame rate of the imagers (1/Ns), where N is the maximum image transfer rate in frames per second(fps). This means that during 1-1/N s, the LEDs will be on stand-by. Thepower consumption of the LEDs then depends on the maximum current at aparticular frequency and duty factor, and the stand-by currentrequirements thereof. FIG. 3 shows a timing diagram for an imager and anLED, wherein LED power consumption may be minimized. The LEDs operateduring the same period that the imagers are collecting data, after whichtime period both the LEDs and the imagers are shut down.

Transcutaneous induction, as an example, may be useful for providingadditional power. That is, the capsule would contain a coil in which acurrent could be induced by a changing magnetic field generated by atransmitter worn by the patient. Upon rectification, this current couldbe used to charge the batteries, whereby the battery may be dischargedand charged with the consequence of improving the life of the battery.

As an example of current usage, estimating LEDs at 75 mA (for 3);imagers at 118.2 mA; and RF transmitters at 9.1 mA, one obtains a totalof 192.3 mA without including the controller and multiplexer. Thesevalues were quoted from commercially available products: for MT9V 403,as an example, with the imagers and the RF transmitter assumed to beoperating at the highest tolerable temperature, etc.

The batteries may be activated after the outer protective coating orshell of capsule 10 is dissolved in the colon by a switch or othermechanism (not shown in FIG. 1 hereof) adapted for such purpose. See,for example, U.S. Pat. No. 6,635,834 for “System and Method to DelayClosure of a Normally Closed Electrical Circuit” which issued to JustinBernard Wermer on Oct. 21, 2003, for a description of a device forallowing an electrical circuit to close when a material holding thecircuit open is exposed to an environment having a specific pH.

Expandable Components: Expandable material is disposed at each end ofthe shell in the embodiment shown, but may be provided at one end only.It provides stability to the imaging modality upon expansion. Theproperties of the expandable material should enable it to (1) expandextensively; (2) expand in a relatively short amount of time; (3) exertreasonable pressure on the walls of the lumen; (4) be biocompatible and(5) have a stable consistency.

Once the colon has been reached, the coating of the capsule dissolvesand the expandable material starts to expand. The expansion thus startsin the cecum. The average diameter of the colon is about 6.5 cm [See,e.g., Thomas McCracken, New Atlas of Human Anatomy, New York, Barnes &Noble Books, (1999).]. For the expandable material to touch the walls ofthe colon upon expansion or at least have a similar capsule diameter tolumen diameter ratio for the small bowel capsule endoscopy (the diameterof the present capsule is 1.1 cm while that of the small bowel is 2.5 cm[See, e.g., McCracken, supra.]), 200-500% expansion is needed. Thisamount of self-expansion may be achieved using for example either of twomechanisms, as examples: (1) diffusion of water molecules by osmosis,which can be observed in hydro-gels, certain polymeric materials andmineral clays; and (2) release of potential energy resulting in anexpansion of the material possessing the potential energy, which can beobserved whenever a compressed or stretched material is released. Stentsand springs are examples of this effect.

It should be mentioned that if a larger lumen organ is to be imaged, forexample, the stomach, stabilization of the capsule would require asignificant expansion of the expandable material, thereby preventing thestabilized capsule from passing into the duodenum. In U.S. PatentApplication Publication No. US2004/0192582A1 for Ingestible FormulationsFor Transient, Noninvasive Reduction Of Gastric Volume, by Daniel R.Burnett and Peter G. Edelman, expandable materials are described thatare effective for being trapped in the stomach, while slowly dissolvingtherein such that they eventually pass into the duodenum.

The more rapid the expansion, the more rapidly the imaging capsule maybe stabilized in the colon, thus allowing quality imaging of the organas soon as the capsule enters the colon. The rate of expansion inosmosis depends on numerous factors, including the structure of thematerial, the membrane and the concentration of the solution. Bycontrast, the release of potential energy is rapid.

The pressure exerted upon expansion on the walls of the colon should notdamage this organ. The net pressure that the walls of the colon canbear, P_(net), can be calculated using the following equation [See,e.g., Ferdinand P. Beer and E. Russell Johnston, Jr., Mechanics ofMaterials (England: McGraw-Hill Book Co., Metric Edition, 1992).],assuming that the pressure applied on the walls would only result in ahoop stress and no longitudinal stress:

${P_{net} = {\sigma_{T}\frac{t}{R}}},{and}$${P_{s \cdot \max} = {{\sigma_{T}\frac{t}{R}} + P_{peristalsis}}},$

where

P_(net) is the net pressure that the walls of the colon can bear uponexpansion; P_(s max) is the maximum swelling/expanding pressure on thewalls of the colon upon expansion; σ_(T) is the tensile strength of thecolon; t is the thickness of the colonic walls; R is the inner radius ofthe colon; and P_(peristalsis) is the peristaltic pressure in the colon.It should be noted that the net pressure applied on the walls of thecolon is the difference between the maximum swelling/expanding pressureapplied by the expandable material, P_(s) max and the pressure exertedby the colonic walls on the device, peristalsis as shown in the equationfor P_(net) above. The difference between the maximum swelling/expandingpressure, P_(s max) and the peristalsis pressure, P_(peristalsis),should be less than the net pressure, P_(net) so that no harm is causedto the colonic walls.

The expandable material should not being toxic and not causeinflammation or immunological ejection. The expandable material shouldnot be permanently deformed by the peristaltic pressure. It should beable to deform under pressure but regain its original shape when thepressure is removed. The expanded material should also keep itsconsistency and not change state under the influence of water or colonicfluids.

Materials having desired properties were categorized according to theirmechanism of expansion: osmosis, or the release of potential energy. Thelatter mechanism has proven to b effective in several medicalapplications such as stents that help relieve pathological obstructionof tubular structures in vascular, urologic and gastroenterologicalsystems and self-expanding prostheses [See, e.g., Lauto et al.“Self-expandable chitosan stent: design and preparation”, Biomaterials,22, pp. 1869-1874 (2001).]. The concern with this mechanism is the shapeand structure of the expanded material. Stents and other prostheses aremostly hollow at the center and the smooth traveling of the device bynatural peristalsis in the GI tract is not guaranteed. The availabilityof stent structures that can resist the peristaltic motion in the colonwithout themselves moving makes osmosis the preferred mechanism for theproposed apparatus [See, e.g., “Medical stents for body lumensexhibiting peristaltic motion”, U.S. Pat. No. 6,505,654, which issued toAndersen et al. on Jan. 14, 2003.].

The expandable material and the casing onto which it is attached ischosen to enable the prediction of the expanded volume, as well as toensure that the expandable and imaging components do not becomeseparated as a result of shearing. FIG. 4 shows expandable material 16 battached to one end of cylindrical capsule 10 illustrated in FIG. 1hereof. Expandable material 16 b is shown in its expanded state, andheld in place by adhesive material, 34, which will be described in moredetail hereinbelow. From the parameters identified in FIG. 4, the volumeof the expandable material can be predicted by the following equation:

$V = {{( \frac{{- {KC}} + B}{C^{2}} )^{2}\frac{C^{5}}{5}} + {K^{2}\frac{C^{3}}{3}} + {B^{2}C} + {2( \frac{{- {KC}} + B}{C^{2}} ){C^{4}( \frac{K}{4} )}} + {2( \frac{{- {KC}} + B}{C^{2}} )\frac{C^{3}}{3}B} + {2K\frac{C^{2}}{2}B}}$

where K is the slope of the inclination of the casing or expandablecomponent; C is the coordinate of the expanded material that crosses thehorizontal axis; B is the coordinate of the expanded material thatcrosses the vertical axis; and V is the volume of the expanded material.

Bentonite is composed of smectite clay minerals which have propertieswhich are related to their chemical composition, atomic structure, andmorphology [See, e.g., R. E. Grim and N. Guven, “Properties and Uses ofBentonite”, in Bentonites: Geology, mineralogy, properties and uses,Elsevier Scientific Publishing Company Amsterdam, pp. 217-248 (1978).].The most important characteristic of bentonite is its potential to swellunder the effect of a solvent, for example, water, due to the packetstructure of the stratified bentonite See, e.g., Wieczorek et al.,“Comparative Characteristics of Local an Foreign Bentonites” , Macromol.Symp. 194, pp. 345-350 (2003)1. Other properties of bentonite include:(1) biocompatibility; (2) extensive swelling; (3) rapid swelling; (4)ability to exert a reasonable swelling pressure on the walls of thelumen; and (5) ability to withstand the pressure in the colon whileremaining attached to the imaging component and keeping its consistency.

Natural minerals such as montmorillonite have been utilized asenterosorbents for withdrawing toxic and pathogenic components from thebody of warm-blooded animals and humans. Acceptable daily doses of thisnatural mineral range between about 0.1 and 1.0 g per kg of body weight.U.S. Pat. No. 6,287,576 B1 for “Biostimulating Agent”, which issued toBgatov et al. on Sep. 11, 2001, describes a biostimulating agent thatcomprised of natural minerals containing not less than 2 weight (wt) %of montmorillonite. Therefore, the bentonite to be used for the proposedapparatus may contain greater than 92 wt % of montmorillonite in orderto ensure its biocompatibility.

Bentonite contains montmorillonite, feldspar, quartz, etc., and theswelling of bentonite is caused by the swelling of the montmorillonitewhich is a swelling clay mineral. The montmorillonite mineral is a 2:1layer consisting of an octahedral sheet sandwiched between two silicasheets as explained by Hideo Komine, in “Simplified evaluation forswelling characteristics of bentonites”, Engineering Geology, 71, pp.265-279 (2004). Interlayer water and exchangeable cations exist betweenthe montmorillonite layers. Water is absorbed into the interlayers,resulting in expansion. The swelling pressure and swelling deformationof bentonite containing montmorillonite minerals are thus considered tobe caused by the repulsive forces that occur between the layers. So, theswelling characteristics of bentonite can be evaluated by observing theswelling behavior of montmorillonite in bentonite [See, e.g., Wieczoreket al., supra].

The swelling characteristics of bentonite are characterized by theswelling pressure and swelling deformation. Komine (2004), supra,proposed a simplified method for evaluating the swelling characteristicsof bentonite. The parameter “swelling volumetric strain ofmontmorillonite”, ε*_(sv), was earlier introduced by Komine and Ogata[See, H. Komine, and N. Ogata “Experimental study on swellingcharacteristics of sand-bentonite mixture for nuclear waste disposal”,Soils and Foundations, 39, no.2, pp. 83-97 (1999)] to syntheticallyevaluate the swelling characteristics of bentonites (ε*_(sv) is thepercentage volume increase of swelling deformation of montmorillonitewhen dry.). Komine (2004), supra, used equations derived by Komine andOgata (1999), supra, to propose the simplified method.

It was found that the swelling characteristics of bentonites arestrongly dependent on both the kinds of bentonites and the dry density.According to Komine (2004), supra, using the above-mentioned equationswith the parameters derived from the type of bentonite used and its drydensity, the swelling volumetric strain ε*_(sv) (%), can be calculatedfrom:

${ɛ_{sv}^{*} = {\frac{V_{v} + V_{sw}}{V_{m}} \times 100(\%)}},$

where V_(v) is the volume of voids in the composite material; V_(sw) isthe maximum swelling deformation of the composite material at constantvertical pressure (V_(sw)≧0); and V_(m) is the volume of montmorillonitein the composite material.

From the experiments described by Komine (2004), the relationshipsbetween maximum swelling pressure and ε*_(sv) and and applied verticalpressure, and ε*_(sv) can be obtained. Additionally, it should be notedthat if the vertical pressure is greater than 200 KPa, the relationshipsbetween σ_(v) and ε*_(sv) are almost the same for all kinds ofbentonite. From these graphs, and using the calculated value ε*_(sv) themaximum swelling pressure and maximum swelling strain can be obtained.Evaluating flow and swelling characteristics of buffer and backfillmaterials may also be found in Komine (2004), supra.

Typical curves of swelling strain versus time at chosen bentonitecontents have a hyperbolic shape [See, e.g., Komine 2004, supra]. It maybe observed that a maximum swelling strain, ε_(s max), value, where

${ɛ_{s\mspace{11mu} \max} = {\frac{V_{sw}}{V_{v} + V_{solid}} \times 100(\%)}},$

and V_(sw) and V_(v) are defined hereinabove, and V_(solid) is thevolume of the composite material excluding voids, is reached after aperiod of time. The maximum swelling strain, ε_(s max), can becalculated from the asymptotic line of the hyperbola given by theequation:

$ɛ_{s\mspace{11mu} \max} = {{\frac{\lim}{ tarrow\infty }( \frac{1}{\frac{a}{t} + b} )} = {\frac{1}{b}\mspace{14mu} {(\%).}}}$

It is known that the maximum swelling pressure depends on the initialdry density of the bentonite. It may also be noted that the time takenfor this particular bentonite, Neokunibond (containing 76%montmorillonite), to reach maximum swelling pressure is less than 1000min. Assuming that the slope before maximum swelling pressure is reachedis linear, an equation relating swelling pressure and time can beobtained. The swelling pressure at a particular time can thus beobtained and the volumetric swelling strain, found from a graph ofmaximum swelling pressure versus swelling volumetric strain.

Both the ionic concentration of pore water and the specific surface ofbentonite are known to influence the swelling characteristics of soils[See, e.g., H. Komine and N. Ogata, “New equations for swellingcharacteristics of bentonite-based buffer materials” CanadianGeotechnical Journal, 40, pp. 460-475 (2003).]. In this reference, theauthors proposed new equations for evaluating the swellingcharacteristics of bentonite-based buffer material by considering theinfluences of sand-bentonite mass ratio and the exchangeable-cationcompositions in bentonite. It was also found that the swellingcharacteristics of the buffer material are significantly influenced bythe chemical conditions of the bentonite and the surroundings [Komineand Ogata (2003), supra]. Komine (2004), supra, however found that themaximum swelling pressure is strongly influenced by the montmorillonitecontent rather than the exchangeable-cation compositions in bentonite.The effects of ions on the swelling characteristics can thus be ignoredand the method proposed by Komine (2004), supra, used.

To prevent clogging of the expanded material in the colon, a maximumexpansion of about 300% is needed to ensure that the expanded material'sdiameter does not exceed the smallest diameter of the colon. Usingbentonite containing greater than 92 wt % of montmorillonite withdifferent dry densities, the experiments described by Komine (2004),supra, can be performed to obtain graphs of swelling pressure versustime and maximum swelling pressure versus swelling volumetric strain.According to these graphs, depending on the swelling volumetric strain(and hence, on the volume expanded), a bentonite with a particular drydensity is chosen such that the desired expanded volume can be achieved,and the maximum swelling pressure of bentonite reached in a minimumamount of time. The maximum swelling pressure should also be less thanthe net pressure that the colonic walls can bear. In order to achievethe purposes of the present invention, the bentonite should be firmlyattached to the capsule bearing the imagers and associatedmicroelectronic components; therefore, the bentonite may be mixed withappropriate biocompatible polymers in effective amounts to achieve therequired bonding strength [See, e.g. U.S. Pat. No. 6,153,222 for“Volume-Expandable, Sheet-Like Application Form Suitable As An ActiveSubstance Carrier, In Particular For Oral Application,” which issued toFrank Becher on Nov. 28, 2000]. Expandable biocompatible polymers mayalso be used in the absence of bentonite. For example, microcrystallinehydrogels and polyolefins may be used. Carboxymethyl cellulose may alsobe used.

Adhesive Components: The adhesive material ensures that the expandablepart remains attached to the imaging component throughout the capsule'stravel in the GI tract, especially the colon. Due to the geometry of thecapsule and pressure applied in the colon, there is a risk of the twocomponents detaching from each other. The breaking strength should thusbe greater than the maximum pressure applied in the colon which wouldarise if the peristaltic pressure holds one end of the expandablematerial fixed while random pulling pressure is applied on the remainderof the capsule. The random pressure is assumed to have a pulling effect;that is, a lateral pressure of the same magnitude as the transversallyapplied random pressure. The worst-case scenario would be where one endis fixed and the other is pulled laterally. It was found that the meanpeak amplitude of antegrade propagating pressure waves for all colonicregions is significantly greater than that of the retrograde propagatingpressure waves [See, e.g., Ian J. Cook et al., “Relationships betweenspatial patterns f colonic pressure and individual movements ofcontent”, Am. J. Physiol. Gastrointest. Liver Physiol., 278: G329-G341(2000)]. The mean peak amplitude of antegrade propagating pressure wavesis 41.8±2.3 mmHg; range 5-169 mmHg [See, e.g., Ian J. Cook et al.,supra.]. A value of 300 mmHg (40 KP) is used to calculate the worst-casescenario for the present design.

The peristaltic pressure in the colon applied to various components ofthe capsule results in shearing that might cause the components to bedetached from each other. The casing of the imaging component as beenspecially designed, not only to predict the expansion, but to make theexpandable material fit more tightly in the casing upon expansion, thuspreventing the expandable and imaging components from being detached asa result of shearing. Hence, in choosing an adhesive material, theshearing effect caused by the transversal peristaltic pressure can bedisregarded.

The adhesive material should also be biocompatible. A cyanoacrylateadhesive was approved by the FDA in the U.S. in 1998 for Topical use toclose skin incisions and lacerations [available from Protein PolymerTechnologies Inc. of San Diego, Calif.]. Therefore, such adhesive isbiocompatible. Moreover, cyanoacrylate adhesives set fast and have highstrength. Several cyanoacrylate adhesives are available commerciallyhaving various breaking strengths. For the present apparatus, acyanoacrylate adhesive manufactured by TOAGOSEI Co., Ltd of Tokyo,Japan, named Aron Alpha 201, and having a breaking strength of 12.75 MPamay be chosen. This breaking strength is, therefore, greater than themaximum applied lateral pressure of 40 KPa. However, any suitableadhesive having the indicated properties may be used.

To avoid undesirable separation of parts of the expandable material fromthe main body of the expandable material, the expandable material may beencased in a liner. As shown in FIGS. 5 and 6, the liner is formed froman inner liner 40 and outer liner 42. The inner liner 40 is bonded tothe capsule 10 with adhesive and remains in the same place duringexpansion of the expandable material 16. The outer liner 42 is foldedabout the outer periphery of the expandable material 16, as shown inFIG. 5, and expands as shown in FIG. 6 when the expandable material 16is exposed to fluids of, for example, the colon, after dissolution orbreaking of the coating 11. The outer liner 42 is sufficiently permeableto allow access of colon fluids to the expandable material 16, and mayfor example by made of spun bonded poly propylene or cotton. The innerliner 40 is preferably impermeable to fluids and may be made for exampleof a plastic film. The expandable component 16 may also include fillersuch as wood pulp. The coating 11 may extend all around the capsule 10or may extend only as far around the capsule as required to secure theexpandable material 16.

The foregoing description of the invention has been presented forpurposes of illustration and description and is not intended to beexhaustive or to limit the invention to the precise form disclosed, andobviously many modifications and variations are possible in light of theabove teaching.

The capsule is swallowable and thus should have smooth edges. Thecapsule may be any suitable shape such as cylindrical with domed ends,oblate, oval in cross-section, spherical, spherical-like, saucer,saucer-like, etc. The expandable material need only be placed on oneside (as shown in FIG. 4), although an embodiment with the expandablematerial on both sides of the capsule has been described as an example.One or more imagers may be placed around the circumference of thecapsule. If there is expandable material only on one side, one or moreimagers may be longitudinally positioned at the opposite side of thecapsule to the expandable material. If there is only one piece ofexpandable material, it may be largely spherical. It should beunderstood that references to spherical or cylindrical describe theapproximate shape of the object. If the expandable material has aspherical shape when expanded, the expandable material will look morelike a saucer when squeezed by the walls of the organ. The capsule wallmay be entirely transparent, or a window or other sufficientlytransparent portion may be provided in the capsule wall for the imager,preferably with appropriate lenses to ensure that an adequate image iscollected by the imager. Preferably, the imager should not contact thewalls of the organ. A person of average skill in the art may deviseother methods for controlling the release of the expandable materialbased on the present disclosure. A particular method of controlling therelease has been disclosed. It is possible also to store imagescollected by the imager on board the capsule for later retrieval.

The embodiments were chosen and described in order to best explain theprinciples of the invention and its practical application to therebyenable others skilled in the art to best utilize the invention invarious embodiments and with various modifications as are suited to theparticular use contemplated. It is intended that the scope of theinvention be defined by the claims appended hereto. In the claims, theword “comprising” is used in its inclusive sense and does not excludeother elements being present. The indefinite article “a” before a claimfeature does not exclude more than one of the feature being present.

1-16. (canceled)
 17. An apparatus for imaging walls of agastrointestinal organ, the apparatus comprising: a swallowable capsule;an imager coupled to the capsule; and an absorbent material attached tothe capsule and capable of swelling due to absorption ofgastrointestinal fluids; where the expandable material is configured toswell to stabilize the capsule in the gastrointestinal organ.
 18. Theapparatus of claim 17, wherein the capsule has a window for passage oflight radiation into the imaging system.
 19. The apparatus of claim 17,wherein the expandable material comprises a first expandable materialportion and a second expandable material portion.
 20. The apparatus ofclaim 19, wherein the first expandable material portion and the secondexpandable material portion are attached to opposed ends of the capsule.21. The apparatus of claim 17, where the capsule has an elongated shapeand the absorbent material is not coupled to or covering at least oneportion of a longitudinal center of the capsule.
 22. The apparatus ofclaim 17, further comprising: a controllable releasing mechanismconfigured to substantially prevent swelling of the absorbent materialuntil the apparatus reaches a desired location in a patient'sgastrointestinal tract.
 23. The apparatus of claim 21, wherein thecontrollable releasing system comprises a material that is configured torelease the absorbent material at the desired location.
 24. Theapparatus of claim 23, wherein the controllable releasing systemcomprises a component that dissolves in the presence of fluids at thedesired location.
 25. The apparatus of claim 21, wherein thecontrollable releasing system comprises an outer component for sealingthe capsule and the absorbent material, and adapted to dissolve or breakwithin the gastrointestinal organ, but not in other gastrointestinalorgans, thereby permitting swelling of the expandable material such thatthe capsule is laterally stabilized within the targeted gastrointestinalorgan while being able to move through the gastrointestinal organs. 26.The apparatus of claim 21, further comprising: a light source.
 27. Theapparatus of claim 26, further comprising: a wireless transmitterconfigured to transmit images of the walls of the gastrointestinal tractto a receiver.
 28. The apparatus of claim 26, where the light sourceincludes a light emitting diode adapted for illuminating a portion ofthe walls of the gastrointestinal organ.
 29. The apparatus of claim 26,further comprising: a controller configured to control the operation ofthe light source and imager.
 30. The apparatus of claim 17, furthercomprising: a plurality of light sources and imagers arrangedcircumferentially around the capsule.
 31. The apparatus of claim 30,further comprising: a controller configured to control the operation ofthe light sources and imagers.
 32. An apparatus for imaginggastrointestinal organs, the apparatus comprising: a swallowable capsulehaving an absorbent material attached to the capsule, the absorbentmaterial capable of swelling due to absorption of gastrointestinalfluids to stabilize the capsule in a gastrointestinal organ; an outercomponent sealing the capsule and the absorbent material, the outercomponent adapted to dissolve or break within a targetedgastrointestinal organ, but not in other gastrointestinal organs,thereby permitting swelling of the expandable material such that thecapsule is laterally stabilized within the targeted gastrointestinalorgan while being able to move through the gastrointestinal organs; atleast one light source configured to illuminate a portion of theinterior of the targeted gastrointestinal organ; at least one imager forimaging the internal wall of the targeted gastrointestinal organ, andgenerating signals bearing the images of the internal wall; a wirelesstransmitter in the capsule; and at least one controller configured tocontrol the operation of the at least one light source and the at leastone imager.
 33. A method for imaging gastrointestinal organs, the methodcomprising: introducing a capsule into the gastrointestinal tract of apatient, the capsule including an imager configured to obtain images ofthe internal walls of gastrointestinal organs through which the capsulepasses; activating the imager of the capsule to capture images of theorgan of interest; where, during at least activation of the imager, thecapsule is stabilized by an absorbent material that is coupled to thecapsule and is in expanded state due to absorption of gastrointestinalfluids.
 34. The method of claim 33, further includes wirelesslytransmitting at least one captured image from the capsule while thecapsule is disposed in the gastrointestinal tract.
 35. The method ofclaim 34, where the absorbent material is not permitted to absorbgastrointestinal fluids until the capsule reaches the organ of interest.